Polyimide optical waveguides fabricated with electron beam lithography

Fabrication Technique of a Nonlinear Optical Structure Using Optical Polymeric Films by Direct Electron-beam Irradiation

A simple fabrication technique of nonlinear optical structures for use with dye-doped polymer is described. Polymethylmethacrylate, U-100 polymer, and polystyrene were used as the host matrices to fabricate the nonlinear optical waveguide. The periodically poled nonlinear optical polymer structures and ridge-type channel structures were fabricated by direct electron-beam irradiation. The electron beam with 25 kV of energy was exposed directly onto the polymer films containing the nonlinear optical chromophores. We can also demonstrate the fabrication technique of the domain-inverted grating of dye-doped polystyrene film.

Simultaneous fabrication of optical channel waveguides and out-of-plane branching mirrors from a polymeric slab structure

Recently, polymeric multimode optical waveguides have been widely studied for low-cost interconnection use. We describe fabrication processes for a low-loss poly(methyl methacrylate) (less than 0.1 dB/cm at 675 nm) waveguide based on the reactive-ion-etching technique and for a slope (45 degrees mirror face) formed on the waveguide. To obtain a ridge core with a crack-free and extremely smooth surface, we applied a heating process at a temperature greater than the glass transition point and a smoothening process by solvent. Furthermore, to fabricate simultaneously both vertical and sloped sidewalls, we applied a unique phenomenon in the process that decreases the etching rate directly under a narrow opening of etching mask. By using the above fabrication techniques, we demonstrated an out-of-plane branching mirror.

Channel-optical-waveguide fabrication based on electron-beam irradiation of polyimides

A new-channel-waveguide-fabrication process for use with polyimide is described. The new technique uses an electron-beam-induced effect to alter the refractive index of the polyimides directly. Channel waveguides with an 8-µm-wide, 8-µm-deep core have been fabricated on a polyimide film by the use of electron-beam irradiation. Only one kind of polyimide (6FDA/TFDB) was used in this waveguide. The difference in refractive index between the core and the cladding was approximately 0.30% for both TEand TM-polarized incident light when the dose was 1500 µC/cm(2), which was sufficient to produce waveguides. The optical properties of the waveguide are also demonstrated.

Fabrication of large-core, high-Δ optical waveguides in polymers

The realization of polymer optical waveguides that have a large core size and high refractive-index difference (LCHD) Δ transmission characteristics is presented. A fabrication procedure for the waveguide based on vertical dip coating and reactive ion etching has been studied. To achieve the lower propagation loss, this procedure includes two original techniques, i.e., the lamination of thick polymer films and sidewall flattening. With these techniques, Δ of 5.4% and a 80 µm × 83 µm core polymer waveguide with 1.4-dB/cm propagation loss were achieved at 680 nm. The LCHD polymer waveguides are useful for practical power-transmission devices.

Humidity dependence of the birefringence in poly(methyl methacrylate) waveguides

A humidity-dependent birefringence in a poly(methyl methacrylate) waveguide has been observed. This dependence was determined by coupling both a transverse electric and a transverse magnetic mode into a waveguide and then measuring the relative phase at the output. With this method, values for δ(TM) - δ9(TE) were found within the range of 5-90% relative humidity (RH). From the obtained data, Δ(n(TE) - n(TM))/ΔRH as a function of humidity was calculated and plotted.